Human T cell lymphotropic virus-type III (HTLV-III) has been isolated from many patients with acquired immunodeficiency syndrome (AIDS). More than a hundred isolates have been obtained and although genetic variants with different restriction enzyme restriction maps have been observed sera from more than 90% of patients with AIDS or AIDS-related complex (ARC) contain antibodies reactive with the prototype isolate H9/HTLV-III-82. J. Schupbach et al. Science 224, 503 (1984); M. G. Aarngadharan et al. Science 224, 506 (1984). This not only suggests that HTLV-III is the causative agent of AIDS but also indicates that the anti-HTLV-III antibodies are highly crossreactive with the various genetic variants of the virus.
Groups reported to be at greatest risk of contracting AIDS include homosexual or bisexual males; intravenous drug users and recent Haitian immigrants to the United States. Hemophiliacs who receive blood products pooled from donors and recipients of multiple blood transfusions are also at risk. Clinical manifestations of AIDS include severe immune deficiency which generally involves a depletion of helper T lymphocytes, various opportunistic infections and Kaposi sarcoma. These may be accompanied by malignancies and infections. All AIDS patients die within 2-3 years of diagnosis. ARC patients may exhibit lymphadenopathy and depressed helper T cell counts; there is not, however, the devastating illness characteristic of full-blown AIDS. It is not now possible to predict who among them will develop the more serious symptoms.
Much of the evidence implicates HTLV-III as the etiological agent of the infectious AIDS. First, there is consistent epidemiology; greater than 80% of the patients with AIDS have antibodies specific for HTLV-III as revealed by Western blot analysis and solid phase immunoassays. Second, there has been reproducible identification and isolation of virus in this disease; as mentioned, more than 100 variants of HTLV-III have been isolated from AIDS patients. Third, there has been transmission of the disease to normal healthy individuals who received blood transfusions from infected blood donors.
Since the identification of HTLV-III as the probable cause of infectious AIDS and the establishment of a permissive T cell line for mass production of the virus, substantial progress has been made in characterizing the virus and in developing of diagnostic methods for the detection of HTLV-III infection. Most notable is the development of solid-phase immunoassays employing inactivated HTLV-III as a whole virus antigen immunoadsorbent for the detection of antibodies against HTLV-III in sera of patients. Such assays have been shown to detect antibodies in more than 80% of sera from patients with AIDS or ARC, or from individuals infected with HTLV-III and thus are useful for diagnosing AIDS and for screening contaminated blood.
Assays employing the whole virus, however, have several drawbacks. Large quantities of the virus must be cultivated as supply for test reagents. Although rigorous safety measures can be instituted, there are dangers associated with large scale cultivation of the infectious virus. Further, there exists a risk, however small, that test reagents prepared with the inactivated virus can be contaminated with live virus. Thus, persons who handle the reagents may be subjected to the risk of HTLV-III infection.